PH7C0PHTTA. 163 



Practical Studies. — {a) Study the tissues of Laminaria and other 

 kelps in cross and longitudinal sections. 



(6) Make sections through the patches of zoOsporangia (" fruits ") 

 and examine the zo5sporangia and paraphyses. 



(c) Where fresh material cannot he secured, the kelps may be 

 studied very well from alcoholic specimens, which can be obtained 

 from dealers in botanical supplies. 



Systematic Literature. — Farlow, Marine Algae of New England, 

 61-98. 



The study of the Dictyotese may well be omitted by the 

 beginner. 



Okder 9. FirCOIDEa;. The Eockwbeds. 



288. The plants of this order are entirely marine. In 

 some cases the development of the plant-body is unusually 

 perfect, showing a differentiation into parts which have a 

 close resemblance to roots, stems, and leaves. In size they 

 approach the flowering plants. Their tissues, too, show a 

 high degree of differentiation ; the cells are arranged in 

 cell-masses, and these arc differentiated into several varie- 

 ties of parenchyma, approaching, in some instances, to the 

 condition which prevails in the Mosses and their allies. 



289. "With the foregoing there is found a marked differ- 

 entiation of portions of the plant-body into general repro- 

 ductive organs, analogous to the floral branches of higher 

 plants. The sexual organs are developed upon modified 

 branches, which differ more or less in shape and appear- 

 ance from the ordinary ones. 



290. In common Eockweeds (Fucus) of the seashore the 

 sexual organs are found in the thickened ends of the lateral 

 branches {A, Fig. 90). They occur on the walls of cavi- 

 ties termed conceptacles, which are spherical, with a small 

 opening at the top {B, Fig. 90). The conceptacles are at 

 first portions of the general surface, and afterward become 



